DANGEROUS INTERNATIONAL FOREST TREE DISEASES 17 



Polyparus dryophilus Berk., causing white pocket rot of oak heart- 

 wood, with a considerable loss in wood volume. 



Loranthus europeus Jacq.. a mistletoe with yellow fruits, contribu- 

 ting in oak dying back. 



Populus 



Dothichiza poptdea Sacc. & Br., a widespread parasitic fungus, 

 causing necrosis of bark tissue of many poplars, and generally high 

 mortality of 2- to 3-year plants. 



Tentvria populma (Vuill.) Fabr.. producing withering of suc- 

 culent shoots of black poplars in nurseries and plantations. 



Venturia trenvulae Aderh.. producing similar effects as the preced- 

 ing organism on Populus trermda^ P. alba, and varieties of the latter 

 species. 



Melampsora dllii-populina Kleb.. a widespread heteroecious fungus, 

 causing rust and premature defoliation of poplar leaves, mainly on 

 species, cultivars. and clones belonging to the section Aigeiros. 



"Brown spot disease" is to be added although its true agent still 

 remains unknown. The phenomenon is particularly pronounced in 

 euramerican cultivars. but occurs in native poplars also. It spreads 

 continually. 



Other work I did was to register those pathogens dangerous to 

 the other native and foreign tree species grown in the south. The 

 recent trend toward the establishment of test plantations of intro- 

 duced fast-growing species such as pine. oak. larch, and Douglas-fir 

 varieties in a number of southern countries will soon provide better 

 information on the susceptibility of these species to native diseases. 

 Observations until now have been made only in the few existing plan- 

 tations and sometimes only on the rare individual. The identity of 

 native pathogens found on foreign trees will be included in the com- 

 pleted list of pathogens of southern and eastern Europe. 



Czechoslovakia 



Aug. Kalaxdra 



Ordinary Member, Czechoslovakia Academy of Agricultural Sciences. 

 Zbraslav-Strnady, CSSR 



Only a few different introduced tree species are used in Czechoslovak 

 forestry. Some of the larger forest stands in Bohemia are composed 

 mainly of the introduced Pirvus strobus which reaches mean or older 

 age. Larix Isptolevis is grown more frequently but not on a large scale. 

 Introduced spruces are not grown on a large scale either. Douglas-tu- 

 bas been and still is in high favor. In more recent years Abies grandis 

 has been tried. Among the introduced broad-leaved trees, (/>/■ 

 rubra and Fraximus americana are represented here and there. Vari- 

 ous North American. European, and Asian species or lrybrids of poplar 

 have also been introduced. 



Diseases known from other countries are important factors in some 

 regions of Czechoslovakia. Cronartium ribicola Dietr. is damaging to 

 P'n» us strobus here and there in forests, parks, and where used as an 

 ornamental. White pine was formerly favored in the Elbe region of 

 Bohemia because of its resistance to Lophodcrmium pimutri 



